Excessive sleepiness may result from several causes one of which is Sleep Disordered Breathing (SDB). Excessive sleepiness may be particularly dangerous for people who have to operate equipment such as cars, trucks, buses or other machinery. There have been a number of fatal accidents recently where truck drivers have fallen asleep at the wheel. It has been subsequently established that the drivers suffered from sleep apnea. Fatigue in general has been identified as a cause of vehicle accidents. It has been suggested that sleepiness or wakefulness tests would be a requirement for drivers before they are allowed to start a long drive or periodically in order to renew their licence, particularly those who have been diagnosed with sleep apnea.
There are a number of tests to measure sleepiness such as the Epworth Sleepiness scale tests, Vigilance tests and Pupillometry.
The Epworth Sleepiness Scale test is based on a series of questions which are asked of the patient. In some forms, the questions may be posed by an administrator who is physically present while the patient answers. In other forms, the questions may be remotely posed, for example, for self assessment via regular mail, the internet or via an embedded device such as the Health Buddy manufactured by Health Hero.
Vigilance tests measure a patient's reaction time and cognitive alertness, which are generally understood to be indicative of a patient's sleep propensity. This type of test is typically administered using a personal computer (PC) and requires that the patient provide responses to displayed indicia via the input devices associated with the PC. The patient's reaction time in providing the response and/or the accuracy of the response to the displayed indicia are measured and stored to determine the patient's level of alertness. For example, the patient is shown a recognizable object on the PC display, and the patient's reaction time in identifying the object and the accuracy of the identification are measured. One form of vigilance test is to have the person perform a repetitive task, such as clicking a button with a finger upon a signal and to monitor the reaction time or accuracy with which the person clicks the button when signaled to do so.
One form of wakefulness test using a finger-based test is described in “Microsleep during a Simplified Maintenance of Wakefulness Test: A Validation Study of the OSLER Test” by Priest et al. in Am. J. Respir Crit Care Med Volume 163, pp 16190-1625, 2001.
One form of fingerprint identification unit is the “Sony Fingerprint Identification Unit” FIU-710.
Pupillometry is based on the observation that the pupils of sleepy individuals display measurable characteristics which are significantly different to the pupils of people who are not sleepy. During pupillometry recording in the dark, the pupils of behaviorally sleepy individuals oscillate widely in size. This phenomenon is named pupillary “fatigue waves”, and is not observed in people who are not sleepy. Low-frequency components are dominant in persons with excessive daytime sleepiness. The amplitude of slow oscillations (typically less than 0.5 Hz) can reach several millimeters. It has also been observed that the pupils of sleepy people became increasingly miotic (decreased in size) with ensuing sleepiness. In contrast the pupils of people who are behaviorally alert maintain a stable size. The phenomenon has been observed by Lowenstein and colleagues and reported in an article entitled “Pupillary movements during acute and chronic fatigue” published in Investigative Opthalmology, 2, 138-157 (1963).
In the article “Pupillographic Assessment of Sleepiness in Sleep-deprived Healthy Subjects” in the SLEEP journal, volume 32, no. 3, 1998 by Wilhelm et al., a method of providing sleepiness measures is described. The contents of this article are hereby incorporated by reference.
In this specification, the term “sleepiness test” is intended to include somnolence and wakefulness tests.
A potential difficulty with the use of these tests in certain applications is that of authenticating the person who is being tested. This may be critical in applications where the person may be required to operate potentially dangerous equipment, such as truck driving, where there may be an incentive for the person to work in spite of being tired. For example, if the Epworth Sleepiness Scale test were to be administered remotely, the person may ask another, presumably non-tired, non-sleepy or more wakeful person to take the test instead and there may be no way to verify who has taken the test. An automatic system for sleepiness testing may be capable of correctly identifying whether or not a person is sufficiently alert to drive, or to undertake a particular task such as operating machinery, however, the system may be defeated if a substitute person takes the sleepiness test.
Similarly sleepiness testing may be administered on a periodic basis to determine whether a user has been compliant with a medical treatment for their condition. A determination of compliance can be useful as part of management of their condition. A user's compliance with medical treatment may also be a precondition for the grant or maintenance of a permit such as a driver's licence. Therefore it would be desirable for a sleepiness test to be conducted on a periodic basis in a location convenient to the user and preferably without the need of attendance by a skilled operator. Ideally the sleepiness test will be capable of self administration by the user.
It is one aspect of the invention to overcome problems with prior art sleepiness tests.